Method for uniform distribution of gases in an annulus and apparatus therefor



Sept. 30, 1969 w. 1 WILSON METHOD FOR UNIFORM DISTRIBUTION OF GASES INAN ANNULUS AND APPARATUS THEREFOR 2 Shets-Sheet l Original Filed June 8,1964 lv Ow FIG.

INVENTOR. WILL/AM L. W/LSON BY "QMNH Qwut Afro/eww.:

Sept. 30, 1969 w. L. wlLsoN 3,469,943

METHOD FOR UNIFORM DISTRIBUTION OF GASES IN AN ANNULUS 'AND APPARATUSTHEREFOR Original Filed June 8, 1964 2 Sheets-Sheet L Flo.: Fla. 4

IWENTOR.

WILLIAM L. WILSON BY we,

A TTORNEYS United States Patent O 3,469,943 METHOD FOR UNIFORMDISTRIBUTION OF GASES IN AN ANNULUS AND APPARATUS THEREFOR William L.Wilson, Barberton, Ohio, assigner to PPG Industries, Inc., a corporationof Pennsylvania Filed Apr. 29, 1968, Ser. No. 725.226

Int. Cl. C01b 13/14; C01g 23/04; B013' 1/14 U.S. Cl. 23--202 10 ClaimsABSTRACT OF THE DISCLOSURE The production of pigmentary metal oxides,e.g., titanium dioxide, by vapor phase oxidation of the correspondingmetal halide, e.g., titanium tetrachloride, is described. The result ofineffective mixing of reactant gases is discussed and a particularmethod for delivering reactant gases to the mixing Zone in a uniformmanner described.

This application is a continuation application of Ser. No. 373,414,filed lune 8, 1964, and now abandoned.

This invention relates to novel apparatus and process for thedistribution of a gas or gases. More specifically, this inventionrelates to novel apparatus and process for the distribution of a gas orgases in the production of metal oxides, particularly pigmentarytitanium dioxide, by vapor phase oxidation process; that is, thereaction of a metal halide in the vapor phase with an oxygenating oroxygen-containing gas.

In the production of titanium dioxide by the vapor phase oxidation oftitanium tetrahalide either in the presence or absence of a fluidizedbed, titanium tetrahalide is oxidized by reaction in the Vapor phasewith oxygen or an oxygen-containing gas in a relatively confined areamaintained at a temperature above 700 C. in a range of about 800 C. to1200 C., preferably not higher than 1600o C.

An important aspect of eiciently producing or making pigmentary titaniumdioxide is the mixing of vaporous or gaseous reactant streams, e.g.,vaporous TiCl., and oxygen. In the various vapor phase oxidationprocesses, it is especially useful and advantageous to introduce thereactant gas streams of titanium tetrahalide and oxygencontaining gasseparately into the reaction zone by means of a series of concentrictubes or annuli. Reference is made to U.S. Letters Patent 2,791,490issued to Willcox and U.S. Letters Patent 2,968,529 issued to Wilson.

In more sophisticated processes, such as disclosed in U.S. LettersPatent 3,068,113 issued to Strain et al. and U.S. Letters Patent3,069,281 issued to Wilson, additional gas streams, e.g., inert gases,are separately introduced into the reaction zone via additionalconcentric tubes. In such arrangements, the number of concentric tubesemployed will generally be a function of the number of different gasstreams to be introduced into the reaction zone, although it maysometimes be desirable to introduce several gases through a single tube.

Since heat is frequently added to the vaprous reactants or other gaseswithin these tubes, e.g., by reacting CO with O2, or by plasma arc, theconcentric arrangement of tubes may be commonly called a burner and thetubes referred to as burner tubes. Hereinafter, the term gasintroduction tubes will be employed so as not to limit the inventionsolely to burner arrangements; that is, the present invention isintended to be employed in conjunction with any arrangement ofconcentric ow path particularly used in the production of pigmentarymetal oxide by the vapor phase oxidation of a metal halide.

In `accordance with this invention, the various gas streams are emittedfrom annuli flow' paths formed by concentrically arranged tubes in apredictable uniform, concentric iiow pattern and n a direction of owparallel to the axis of the center of the arrangement or assembly of theconcentric gas introduction tubes such that complete and efficientmixing is obtained. By so uniformly and axially emitting the gases fromthe annuli or concentric flow paths, it is further possible to operate apigmentary Ti02 vapor phase oxidation process continuously for longperiods of time without oxide scale or growth forming on the lips of thegas intorduction tubes extending into the reaction chamber.

However, when the process is not operated in accordance with thisinvention, e.g., when one or more of the gas streams is emitted into thereactor at an angle to the axis of the concentric tubes, then oxidescale or growth quickly forms on the lips of the gas introduction tubeseventually causing plugging of the tubes and shutdown of the process.Furthermore, during the growth buildup, part of the scale will break olfin the form of coarse, nonuniform particles which hinder the formationand recovery of a pigmentary metal oxide. Likewise, the growth buildupdiverts the flow of the gases and hinders eiiicient mixing to such anextent that an incomplete reaction results and the formation ofpigmentary metal oxide is further prevented.

In the practice of this invention, such scale buildup or burner growthis prevented and highly-dispersed pigmentary metal oxide, particularlytitanium dioxide, of small, uniform particle size and having improvedtinting strength is produced. More particularly, in accordance with thepractice of this invention, there is obtained a continuous vapor phaseoxidation process wherein complete mixing and reaction of the reactantswithin the reaction zone is achieved with a resulting product havinghighly pigmentary properties.

In the present invention, the inert and/or reactant gas stream isintroduced to the annulus or annuli in a manner such that the gas isdistributed over the entire cross-sectional area of the annulus and isemitted from the burner into the reaction zone in a predictableuniformly concentric flow pattern with a direction of flow parallel tothe `axis of the burner assembly; that is, the present technique makespossible the controllable metering and mixing or" the various gasstreams introduced into the reactor in a predictable, useful, andadvantageous manner.

More particularly, the gas stream is introduced to the annulus by meansof an elongated tube connected substantially transverse to theconcentric tubes assembly, the end of the elongated tube connected tothe concentric tubes assembly containing a deection or distributionplate which directs and distributes the gas throughout thecross-sectional area of the annulus.

The invention will be better understood by reference to the drawing andthe figures thereon.

FIGURE l is a cross-sectional view of a preferred embodiment of thisinvention showing an elongated tube attached to an annulus.

FIGURE 2 is a cross-sectional view of FIGURE 1.

FIGURE 3 is a bottom plan view of the deflector or distribution plateinserted in the elongated tube in FIG- URES l and 2.

FIGURE 4 is a side View of the dellector plate illustrated in FIGURE 3.

FIGURE 5 is a double embodiment of the process of FIGURE 1.

More particularly, in FIGURE 1, there is shown a central tube 1 havingan inside chamber 4 through which a gas or vapor, e.g., a gaseousreactant, preferably oxygen, is introduced from the top in the directionindicated by the arrows. Externally to tube 1 is concentric tube 2,tubes 1 and 2 thereby forming annulus 3 to which a gas is introducedthrough elongated tube 5, the gas being distributed uniformly throughthe cross-sectional area of the annulus by deflection plate 6 such thatthe gas from the annulus 3 is emitted into the reactor R in a uniformlyconcentric ow pattern with respect to the gas stream being emitted intothe reactor from tube 1.

FIGURE 2 is a cross-sectional view of FIGURE l with letters A, B, C, D,E, F, G, H, I, and J indicating the points at which the gas flow in theannulus was meas ured as to be noted hereinafter in the examples.

FIGURES 3 and 4 respectively show a preferred cmbodiment of the gasdeflector or distribution plate 6 to be inserted in tube 5 in FIGURES land 2, one end 7 of the plate 6 being curved in a downwardly directionwith respect to opposite end 8, the corners 9 of end 7 being curvedinwardly as tins.

FIGURE 5 represents a double embodiment of FIG- URE 1 wherein anadditional concentric tube 10 is provided thereby forming a furtherannulus 12, was gas being supplied to the annulus 12 through elongatedtube 11 in which there is inserted a further dellector plate 6.

In the preferred practice of the process as shown in FIGURE 5, anoxygen-containing gas is introduced through tube 4 and the vaporousmetal halide reactant fed into annulus 12 through tube .11. An inertgas, eg., chlorine is fed into annulus 3 through tube 5. Thus, threeseparate and concentric streams are emitted into the reactor R with theinert stream being emitted from annulus 3 serving as a shielding layerbetween the reactant streams being emitted from tube 4 and annulus 12.

In a preferred embodiment of this invention as shown in FIGURES l, 2,and 5, the distribution plate 6 is xed internally within tube 5 andextends into the annulus 3 to a point ranging from it, to 2 inches,preferably 1/16 of an inch to l of an inch, from the innermost diameterof the annulus, that is the outside circumference of tube 1.

In this preferred embodiment, a gas stream is introduced through tube 5toward annulus 3. As the gas stream contacts deflector plate 6, its ilowpattern is split and its velocity and pressure decreased, the gasthereby entering into annulus 3 at a reduced ow rate and pressure andexpanding uniformly throughout the annulus. The gas stream thencontinues in a downwardly direction and is emitted into reactor R in apredictable uniformly concentric flow pattern with respect to the gasemitted from tube 1 and the common axis of tubes 1 and 2.

When the dellector plate is removed from tube S, and gas is introducedinto annulus 3, the momentum of the gas carried a disproportionateamount of the gas to the far side of the annulus 3 opposite the side ofthe annulus at which tube 5 is connected, thereby causing more gas flowthrough the annulus at said opposite side; that is, the gas is notuniformly and predictably distributed within the annulus but flowsdownwardly through the annulus on the side opposite to which it enters.As the gas stream emits into the reaction chamber R, it immediatelyflows at an angle inwardly into the reactant gas stream, eg., oxygen,flowing from tube 1 thereby hindering the emcient and complete mixing ofthe two streams with a resulting oxide growth immediately forming at thelips or exit openings of tubes 1 and 2.

Although it is preferred that tube 5 be substantially transverse orperpendicular to the common axis of the tubes 1 and 2 (as shown inFIGURE l) the tube may be connected at any angle ranging from to 170,preferably 45 to 135.

The width of the deflector plate is at least equal to the radius of tube5, and is preferably equal to twice the radius, that is, the diameter ofthe tube.

The angle at which end 7 is downwardly curved with respect to end 8ranges from 1 to 75, preferable 3 to Corners or fins 9 are curvedinwardly at an angle ranging from 5 to 135, preferably 45 to 90"YAlthough FIGURES l, 2, and 5 illustrate single and double embodiments ofthe present invention, it is understood that additional embodiments maybe employed depending upon the number of concentric tubes, the number ofembodiments generally being equal to the number of tubes minus 1. Thusin the production of pigmentary titanium dioxide, it is possible to useas many as 6 or 8 concentric tubes with 5 to 7 annuli, 4 or more gases,and 6 or more gaseous streams, with some of the gases being introducedin separate streams through 2 or more annuli.

Where the present invention is employed to produce pigmentary titaniumdioxide, the vaporous metal halide reactant, e.g., titanium tetrahalide,is preferably introduced into the reactor chamber from an annulus ortube at a velocity of to 60,000 feet per minute calculated at C. and latmosphere. The oxygen-containing stream is introduced at 25 to 50,000feet per minute calculated as pure oxygen gas at 0 C. and 1 atmosphere.The inert gas, e.g., chlorine, is introduced at 10 to 5000 feet perminute, calculated at 0 C. and 1 atmosphere.

The cross-sectional area of the elongated tube 5 and concentric tubes ispreferably circular. However, it is also possible to employ othergeometric shapes and designs in conjunction with the present process,this being deemed to be within the skill of a mechanic in the art.

Likewise, the present invention may be practiced to introduce anddistribute gas into the central concentric tube, e.g., tube 1 in FIGURES1 and 2. In practice, it is usually preferred to introduce the gasstream, e.g., oxygen, from the top of the tube assembly. However, insome instances, it is necessary to introduce the gas stream at an anglein which case the present invention is valuable to prevent swirling ofthe gas stream; the swirling of the stream also causes poor mixing andthe formation of poor quality pigmentary metal oxide.

In a further modification of the present process, additional reagents ina solid, liquid, or vaporous state, e.g., nucleating and/or rutilepromoting agents, may be introduced into the gas streams flowing throughtubes 5 or 11, eg., by means of a tube connected at an angle to theintroduction tube 5 or 11. By nucleating agents and/or rutile promoteragents, it is meant aromatic hydrocarbons and/or metals which form awhite oxide upon oxidation, eg., aluminum, silicon, and other metalssuch as disclosed in Canadian Patents 631,871 and 639,659 and U.S.Letters Patent 3,068,113. Although metal particles may be employed, itis also feasible to employ the halide or white oxide of the metal.

The temperatures of the various gases introduced through the concentrictubes may range from 100 C. to 2500 C., TiCl4 preferably being below 500C. Whereas the oxygen or an inert gas may be preheated by thecornbustion of a fuel, CO, or sulfur-containing compound to temperaturesin excess of 1500 C., or in excess of 2000 C. where a plasma arc isemployed.

The term inert gas as employed herein means any gas which is inert tothe reaction of the metal halide and oxygen. Examples of such inertgases, not by way of limitation, are argon, nitrogen, helium, krypton,xenon, chlorine, carbon dioxide, or mixtures thereof. Carbon monoxidemay also be introduced in place of, in addition to, or mixed with aninert gas as defined hereinabove, the carbon monoxide being introducedas a means of providing heat to the reaction zone for the sustaining ofthe reaction, the CO reacting with the oxygen to form CO2. Likewise,sulfur-containing compounds as disclosed in United States Letters Patent3,105,742, may be introduced through the annulus or annuli alone ormixed with a gaseous reactant or inert gas. Thus, any gaseous stream,e.g., metal halide, oxygen, inert gas, carbon monoxide,sulfur-containing compounds, natural gas or mixtures of same, may beadded to the annulus or annuli of the concentric tubes by means of thisinvention.

EXAMPLE I A concentric tube arrangement as illustrated in FIG- URES 1and 2 was employed, tube 1 having an outside diameter of 6.75 inches andtube 2 having an inside diameter of 7.50 inches, annulus 3 thereby being0.375 inch wide. Tubes 1 and 2 were 24 inches long. A tube 5 was thenattached to tube 2 at a 90 angle at the axes of tubes 1 and 2, tube 5having an internal diameter of 2 inches.

A gas distribution plate as shown in FIGURES 3 and 4 was inserted intube 5 as shown in FIGURES 1 and 2, the plate being 2 inches wide by2li/32 inches long by 1/16 inch thick, the end 7 being curved downwardlywith respect to end 8 at an angle of about 4. The corners 9 were curved41/2 inch inwardly at an angle of about 85.

An oxygen-containing gas at the rate of 14.3 feet per second (18.75c.f.m.) was introduced through the 2 inch tube into the annulus. Gasilow in feet per second was then measured at varying points in theannulus with the results shown in Table 1.

EXAMPLE II The conditions of Example I were repeated except that thedistribution or deflection plate was removed from tube 5 and the processoperated not in accordance with the invention. Gas flow rate anddistribution was measured at various points in the annulus with theresults shown in Table 1.

EXAMPLE III The conditions of Example I were repeated except that tube 5was 11/2 inches in diameter and the distribution plate was 17/16 incheswide. The oxygen-containing gas was introduced through tube 5 at therate of 25.5 feet per second. The gas rate and distribution was measuredat variouspoints in the annulus with results shown in Table 1.

EXAMPLE IV The conditions of Example III were repeated without thedistribution plate.` The rate of flow through the annulus was measuredat various points and the results shown in Table 1.

TAB LE l The process is operated continuously for over 150 hours. Atypical Ti02 product sample during the run has an average tintingstrength (Reynolds scale) of 1570.

EXAMPLE VI The conditions of Example V 'are repeated without deflectorplate 6 being inserted in the tube 5. After 30 minutes of operation, thetubes 1 and 2 plug at the reactor end thereof due to oxide growth andbuildup. Typical rutile TiO2 product samples during the run have anaverage tinting strength of 1300.

EXAMPLE VII Using the double embodiment process of FIGURES 5, 37gram-moles per minute of oxygen at 1l00 C. is continuously fed throughinternal tube 4 having an internal diameter of 5 inches while 32gram-moles per minute of titanium tetrachloride at 600 C. iscontinuously fed through tube 11 having an internal diameter of 5 inchesinto annulus 12 having a maximum diameter of 12 inches.

One-hundred grams per minute of vaporous aluminum trichloride at 300 C.and 0.19 gram-mole per minute of liquid SCL, is added to the TiCl.,stream before it is introduced through tube 111.

Chlorine at 400 C. is continuously fed at a rate of 6 gram-moles perminute into annulus 3 having a maximum diameter of 8 inches, thechlorine being supplied through tube 5 having an internal diameter of 5inches.

Both tubes 5 and 11 are provided with a deilector plate 6 identical tothat employed in Example I.

The process is operated continuously for over 200 hours without pluggingof the tubes 1, 2, and 1'0 at the reactor end thereof due to oxidegrowth and buildup. Typical rutile TiOz product samples during the runhave an average tinting strength of 1650.

EXAMPLE VIII The conditions of Example VII are repeated withoutdeflector plates 6 being inserted in tubes 5 and 11. After 9() minutesof operation, the tubes 1, 2 and 10 plug at the reactor end thereof dueto oxide growth and buildup. Typical Ti02 product samples during the runhave an average tinting strength of 1425.

Although this invention has been described with particular reference totitanium tetrahalide, e.g., TiCLb TiBr4, and TiI4, it may be employed inthe production of other pigmentary metal oxides.

The term metal as employed herein is defined as including those elementsexhibiting metal-like properties, including the metalloids. Examples,not by way of limitation but by way of illustration, of pigmentary metaloxides which may be produced by the aforementioned process are theoxides of aluminum, arsenic, beryllium,

Flow Distribution in Annulus (Feet per second) at- A B C D E F G H I JExam le I (with distribution plate). 5. 2 5. 7 5. 2 5. 4 5. 9 5. 4 5. 14. 9 5. 8 5. 4 Examgle II (without distribution plat 4. 4 5.8 6. 6 5.35. 8 3. 6 Example III (with distribution plate) 5. 5 5. 3 5. 3 5. 4 5. 65. 3 5. 1 5. 3 5. 5 5. 6 Example IV (without distribution plate) 4. 2 4.8 5. 9 6. 4 6.1 6. 1 f1.3 5. 4 4. 5 4. 2

EXAMPLE V Using the process of FIGURE 1, 37 gram-moles per minute ofoxygen at 1000 C. is -continuously fed through internal tube 1 having aninternal diameter of 5 inches while 32 gram-moles per minute of titaniumtetrachloride with TiCl4 at 600 C. is continuously fed into annulus 3having a maximum diameter of 8 inches, the TiCl4 being fed through tube5 having an internal diameter of 5 inches. Tube 5 is provided with adeflector plate 6 identical to that employed in Example I.

One-hundred to 125 grams per minute of vaporous aluminum trichloride at300 C. and 0.18 gram-mole per minute of liquid SiCl4 is added to theTiCl4 stream prior to the introduction of TiCl.,L through tube 5.

boron, gadolinium, germanium, hafnium, lanthanum, iron, phosphorus,samarium, scandium, silicon, strontium, tantalum, tellurium, terbium,thorium, thulium, tin, titanium, yttrium, ytterbium, zinc, zirconium,niobium, gallium, antimony, lead and mercury.

Likewise, it is to be understood that any of the above teachings may beemployed in any vapor phase oxidation process for providing a pigmentarymetal oxide either in the absence or presence of a fluidized bed.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings.

The above description of the invetnion has been given for purposes ofillustration and not limitation. Various changes and modifications whichfall within the spirit of the invention and scope of the appended claimswill become apparent to the skilled expert in the art. Thus, it will beunderstood that the invention is in no way to be limited except as setforth in the following claims.

I claim:

I.. ln a process for producing pigmentary metal oxide by vapor phaseoxidation of metal halide with oxygencontaining gas in a reaction zonewherein gas selected from the group consisting of reactant gas and inertgas is introduced into an annulus at an angle of from to 170 to thelongitudinal axis of the annulus and forwarded through the annulus tothe reaction zone and wherein the velocity of the gas entering thereaction zone from the annulus is greater on the side of the annulusopposite the side at which gas is introduced therein than on the side atwhich gas is introduced, the improvement which comprises effectingsubstantially uniform gas ow from said annulus into said reaction zoneby deiiecting gas with distribution plate means toward the reaction Zoneas the gas enters the annulus.

2. A process according to claim l wherein the angle at which gas isintroduced into said annulus is from 45 to 135.

3. A process according to claim l wherein the angle at which gas isintroduced into said annulus is substantially perpendicular to thelongitudinal axis of the annulus.

4. A process according to claim` l wherein said annulus is formed byconcentric tubes.

5. In a process for producing pigmentary titanium dioxide by vapor phaseoxidation of titanium tetrahalide selected from the group consisting oftitanium tetrachloride, titanium tetrabromide and titanium tetraiodidewith oxygen-containing gas in a reaction zone wherein gas selected fromthe group consisting of reactant gas and inert gas is introduced into anannulus at an angle of from 10 to 170 to the longitudinal axis of theannulus and forwarded through the annulus to the reaction zone andwherein the velocity of the gas entering the reaction zone from theannulus is greater on the side of the annulus opposite the side at whichgas is introduced therein than on the side at which the gas isintroduced, the improvement which comprises effecting substantiallyuniform gas flow from said annulus into said reaction zone by deflectinggas with distribution plate means toward the reaction Zone as the gasenters the annulus.

6. In a process for producing pigmentary titanium dioxide by vapor phaseoxidation of titanium tetrahalide selected from the group consisting oftitanium tertachloride, titanium tetrabromide and titanium tetraiodidewith oxygen-cotnaining gas in a reaction zone wherein gas selected fromthe group consisting of reactant gas and inert gas is introduced into anannulus at an angle of from 45 to 135 to the longitudinal axis of theannulus and forwarded through the annulus to the reaction zone andwherein the velocity of the gas entering the reaction zone from theannulus is greater on the side of the annulus opposite the side at whichgas is introduced therein than on the side at which the gas isintroduced, the improvement which comprises effecting substantiallyuniform gas flow from said annulus into said reaction zone by defiectinggas with distribution plate means toward the reaction zone as the gasenters the annulus.

7. ln a process for producing pigmentary titanium dioxide by vapor phaseoxidation of titanium tetrahalide selected from the group consisting oftitanium tertachloride, titanium tetrabrornide and titanium tetraiodidewith oxygen-containing gas in a reaction zone at temperatures above 700C. wherein gas selected from the group consisting of reactant gas andinert gas is introduced into an annulus at an angle which issubstantially perpendicular to the longitudinal axis of the annulus andforwarded through the annulus to the reaction zone and wherein thevelocity of the gas entering the reaction zone from the annulus isgreater on the side of the annulus opposite the side at which gas isintroduced therein than on the side at which the gas is introduced, theimprovement which comprises effecting substantially uniform gas ow fromsaid annulus into said reaction zone by deecting gas with distributionplate means toward the reaction zone as the gas enters the annulus.

8. ln a process for producing pigmentary titanium dioxide by vapor phaseoxidation of titanium tetrachloride with oxygen-containing gas in areaction Zone wherein vaporous titanium tetrachloride is introduced intoan annulus at an angle of from 45 to 135 to the longitudinal axis of theannulus and then forwarded through said annulus to said reaction Zone,said annulus being externally concentric to a further annulus into whichoxygen-containing gas is introduced, and wherein the velocity oftitanium tetrachloride entering the reaction zone from the annulus isgreater on the side of the annulus opposite the side at which titaniumtetrachloride is introduced therein than on the side at which it isintroduced, the improvement which comprises effecting substantiallyuniform gas ow from said annulus into said reaction zone by deflectingvaporous titanium tetrachloride with distribution plate means toward thereaction zone as it enters the annulus.

9. In a process for producing pigmentary titanium dioxide by vapor phaseoxidation of titanium tetrahalide selected from the group consisting oftitanium tetrachloride, titanium tetrabromide and titanium tetraiodidewith oxygen in a reaction zone wherein gas selected from the groupconsisting of reactant gas and inert gas is introduced into an annulusformed by concentric tubes at an angle of form 45 to 135 to thelongitudinal axis of the annulus and then forwarded through said annulusto said reaction zone and wherein the velocity of the gas entering thereaction zone from the annulus is greater on the side of the annulusopposite the side at which gas is introduced therein than on the side atwhich the gas is introduced, the improvement which comprises effectingsubstantially uniform gas flow from said annulus into said reaction Zoneby deilecting gas with distribution plate means toward the reaction zoneas the gas enters the annulus.

10. In a process for producing pigmentary titanium dioxide by vaporphase oxidation of titanium tetrachloride in a reaction Zone wherein gasselected from the group consisting of reactant gas and inert gas isintroduced into an annulus formed by concentric tubes at an angle whichis substantially perpendicular to the longitudinal axis of the annulusand then forwarded through said annulus to said reaction zone, andwherein the velocity of the gas entering the reaction zone from theannulus is greater on the side of the annulus opposite the side at whichgas is introduced therein than on the side at which the gas isintroduced, the improvement which comprises effecting substantiallyuniform gas flow from said annulus into said reaction zone by deflectinggas with distribution plate means toward the reaction zone as the gasenters the annulus.

References Cited UNITED STATES PATENTS 1,967,235 7/ 1934 Ferkel.2,240,343 4/ 1941 Muskat. 2,394,633 2/1946 Pechukas et al. 2,635,9464/1953 Weber et al 213-140 2,670,275 2/1954 Olson et al. 3,068,11312/1962 Strain et al 106--300 3,322,499 5/1967 Carpenter et al. 23-139EDWARD STERN, Primary Examiner U.S. Cl. X.R.

